2/4/2013 - Prasad Reduction

This was a reaction that I had learnt in my third year organic chemistry course and has been emphasized quite a bit as a very powerful reaction to control stereoselectivity in reductions.  The Prasad Reduction, first developed in 1984, uses a boron chelating agent to tether the ketone and alcohol together, creating a favored boat transition shape, which is what drives the selection of reduction as seen below.  The reducing agent in this case is sodium borohydride, which attacks the most favorable site of reduction, which can be determined through a simple model of the boat transition state.

Image: Wikipedia

6/11/2012 - Alkene to 1,2-Diol

Alkenes can be used in many sorts of organic reactions, and here is another use in the introduction of alcohol groups onto a molecule. A 1,2-diol is an organic molecule with two adjacent alcohol groups, as seen in the image below, and it is made through the reaction of an alkene with Osmium Tetroxide and a weak base, such as pyridine.  Then there will be a workup of water and sodium bisulfite to protinate the alcohol groups.  As seen below, highlighted in blue, the oxygen atoms come from the same osmium tetroxide molecule, resulting in the alcohol groups being syn to one another (being on the same side of the molecule).

1/26/2012 - Synthesis of Imines from Alcohols Catalyzed by a Ruthenium Complex

     This reaction involves turning a primary alcohol into an imine product with the alleviation of hydrogen gas, catalyzed in the presence of a Ruthenium N-Heterocyclic Carbene complex in the presence of DABCO (which acts as a ligand).  The mechanism is quite complicated but it incolves the exchange of Cl's for H's onto the Ruthenium, and then the addition of the alcohol, followed by the loss of H2, and then the addition of the amine, and then the alleviation of the final imine product.  This reaction was researched by Agnese Maggi and Robert Madsen out of the Department of Chemistry at the Technical University of Denmark.

Picture: from source.

Source: Organometallics 2012, 31, 451−455

12/15/11 - Sharpless Perruthenate Oxidation

   This oxidation reaction is used to turn primary or secondary alcohols into aldehydes or ketones accordingly.  The reactants involved in this reaction are the addition of (Ph3P)2RuCl2 and N-methylmorpholine-N-oxide, or also known as NMO.  What happens here is that the NMO causes the activation of the Perruthenate by oxidizing it, and then the Perruthenate continues to oxidize the alcohol which being bonded to the oxygen of the alcohol.

12/14/11 - Swern Oxidation

     Here is the second oxidation reaction, a more modern method which involves the activation of the DMSO molecule by the oxalyl chloride, which results in the addition of a chloride to the DMSO and then causes the DMSO to add to the alchohol and removing one of the alpha hydrogens.  Turning the alcohol into an aldehyde (or secondary alcohol into a ketone).

11/21/11 - Alcohol Dehydration

     A very simple reaction involving turning an alcohol into an alkene under an E1 elimination mechanism.  This reaction is occurring by the addition of a secondary or primary alcohol with an acid catalyst (a tertiary alcohol will not work because the mechanism requires a proton to come off from the alpha carbon.

Picture: wikipedia

11/20/11 - Hydroboration

    Today, is a simple organic reaction pertaining to the addition of borane (in THF) to an olefin (alkene).  This reaction is then worked up with hydrogen peroxide and a basic environment (usually a source of OH-) to relieve the boron from the carbon and to replace it with an alcohol group.  The mechanistic nature of this reaction calls for the borane into going anti markovnikov due to the fact that it is adopts a partial positive charge as seen below.
  
Pictures: Wikipedia